The most common type used in VHDL is the std_logic. Think of this type as a single bit, the digital information carried by a single physical wire. The std_logic gives us a more fine-grained control over the resources in our design than the integer type, which we have been using in the previous tutorials. Normally,…
You should always use a sensitivity list to trigger processes in production modules. Sensitivity lists are parameters to a process which lists all the signals that the process is sensitive to. If any of the signals change, the process will wake up, and the code within it is executed. We’ve already learned to use the…
In the previous tutorial we used a conditional expression with the Wait Until statement. The expression ensured that the process was only triggered when the two counter signals where equal. But what if we wanted the program in a process to take different actions based on different inputs? The If-Then-Elsif-Else statements can be used to…
In the previous tutorial we learned the main differences between signals and variables. We learned that signals have a broader scope than variables, which are only accessible within one process. So how can we use signals for communication between several processes? We have already learned to use wait; to wait infinitely, and wait for to…
In the previous tutorial we learned how to declare a variable in a process. Variables are good for creating algorithms within a process, but they are not accessible to the outside world. If a scope of a variable is only within a single process, how can it interact with any other logic? The solution for…
Put your skills to the test with this quiz with questions from the first part of the Basic VHDL Tutorial series.
In the previous tutorial, we learned how to use a For-Loop to iterate over an integer range. But what if we want a more detailed control of the loop than just a fixed integer range? We can use a While-Loop for this. The While-Loop will continue to iterate over the enclosed code as long as…
In the previous tutorial we learned to create an infinite loop by using the loop statement. We also learned how the break out of a loop by using the exit statement. But what if we want the loop to iterate a certain number of times? The For-Loop is the easiest way to accomplish this. The…
In the previous tutorial we learned how to delay time using the wait for statement. We also learned about the process loop. We now know that if we let it, the process “thread” will loop within the process forever. But what if we want to do something just once at the beginning of the process?…
In the previous tutorial we learned that a process can be thought of as a program thread. We also learned that a wait; statement causes the program to pause indefinitely. But is there a way to make a program wait for any other time value than forever? If we remove the wait; altogether and try…
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